Storage devices which employ disks with which to store data thereon, such as optical disks, magnetic disks, and/or opto-magnetic disks, are well known. Of these, hard disk drives (HDD) are now in widespread use as external storage devices. In addition, the use of HDDs is not limited to computers, as they are used in many other applications, such as video recording and playback devices, satellite navigation systems, digital cameras, music players, etc.
A HDD generally has a magnetic disk and a magnetic head which accesses the disk and floats on the magnetic disk. The magnetic head generally includes a slider and an element unit (head element unit) on the slider. The smaller the gap between the recording and playback element of the head element unit and the recording layer of the magnetic disk, the greater improvements may be made in the magnetic disk recording density. To this end, efforts to reduce the floating height of the slider body have been made with improvements in data recording density for the HDD.
One way to improve data recording density in a HDD is to narrow the “magnetic spacing,” which is the gap between the recording element/reading element mounted on the magnetic head and the magnetic film formed on the surface of the magnetic disk. The magnetic film may be formed via sputtering or the like. The design value for the clearance between the magnetic disk and the magnetic head, in other words the distance from the protective coating on the magnetic disk to the lowest float point of the magnetic head, has been reduced to a few nanometers in current head designs.
Thus, taking into account a reduction in the floating height of the magnetic head with the increased recording density of the magnetic disk, the possibility of contact occurring between the magnetic disk and the magnetic head is increased greatly. Head/disk contact that occurs in the process of reading or writing can lead to deterioration in performance and the loss of data. Moreover, damage can occur to the head element unit where the impact of the contact is significant. For this reason, a greater smoothness is desired of the magnetic disk to reduce the probability of contact between the magnetic disk and the slider having a lowered floating height.
In the manufacture of a magnetic disk, a burnish process is carried out using a floating head (burnish head) which removes any unnecessary protrusions formed on the disk. The burnish process floats a burnish head on the magnetic disk to remove protrusions from the magnetic disk, using the burnish head to remove any unnecessary protrusions formed on the disk due to foreign objects in the film forming. The burnish process smoothes out the surface of the magnetic disk. Moreover, in the manufacture of the magnetic disk, a glide test may be carried out after the burnish process. The glide test floats a floating head (glide head) on the magnetic disk to test the condition of the magnetic disk surface (the floating condition of the head slider in an HDD), e.g., to determine the smoothness of the magnetic disk surface.
In the burnish process, it is desirable to have the clearance (minimum distance) between the burnish head and the magnetic disk surface as small as possible, in order to improve the smoothness of the magnetic disk. Moreover, to reduce head/disk contact in the HDD, clearance of the burnish head is preferably set to a value close to the clearance in the HDD during use. Furthermore, the glide test is a test of the float condition for the magnetic head in the HDD, so clearance between the glide head and the magnetic disk must be a value close to the clearance in a HDD when the HDD is in use.
A technique to fit the magnetic head with an actuator which adjusts clearance has been proposed to meet the reduced clearances discussed previously. For example, Japanese Patent Publication No. 2009-151890 discloses a technique whereby a heater element is provided in the head element unit, and the clearance between the head element unit and the magnetic disk is adjusted using the heat from this heater element.
As described above, in the burnish process and glide test it is desirable to reduce the clearance between the burnish head/glide head and the magnetic disk. However, it is difficult to obtain a similar clearance to that obtained using the heater element by design improvements to the floating surface of the slider alone. For this reason, it is preferable to carry out clearance control using a heater element in the burnish head/glide head as is used with the head slider in a HDD during use.
However, when a magnetic head mounted in a HDD is used in the burnish process and glide test, it is clear that there is a significant problem with durability during and after testing. There is a desire to reduce element clearance in a HDD. To achieve this, the head element unit may be made to protrude from the remainder of the head due to heat produced by the heater element, such that the tip of the head element unit positioned closest to the surface of the magnetic disk protrudes. When the magnetic head touches the magnetic disk, the head element unit touches the magnetic disk, not the slider body.
When the magnetic head of the HDD is used in the manufacturing of a magnetic disk, the same magnetic head is required to carry out a large number of burnish processes and glide tests on the magnetic disk. However, damage occurs to the head element unit each time head contact occurs, and when there are a large number of contacts between the magnetic head and the magnetic disk, it becomes necessary to change the magnetic head. For this reason, there is a need for a technology to improve the durability of the magnetic head in addition to reducing the clearance between the floating head and the disk in the burnish process and glide test prior to use of the magnetic disk in a HDD.